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Rob, Yes, it is a known fact that you need to align bore the mains when replacing the oil pump, just as you do with any engine, when replacing a rod or main bearing cap. Just because he has "rebuilt" the oil pump, it is not necessarily good. The rebuild kits contain the shaft and gears and bushing, but do nothing to address the wear caused to the pump housing by the gears. As the bushing wears, and the shaft moves a bit off center, the gears wear into the pump housing. When a new shaft and gears are installed, (if there has been excessive wear to the case) there will still be internal leakage in the pump, worse when the oil is warm, due to the excessive clearance between the gears and the pump housing. I certainly cannot confirm or deny the condition of his camshaft and bearing bores from a distance, but as I posted before, unless the wear is considerable, I'll bet there are other contributing factors, such as a weak oil pump. I would check the camshaft jornal diameters, also. If the cam has considerable wear, replacing it would tighten things up a bit. As far as the filter restriction, we have discussed that here before. The oil enters the filter canister from the side, passes inward to the center of the filter, and enters a tiny hole in the side of the center tube of the filter near the top (to allow air that rises to the top to purge). The tiny hole in the side of the center tube acts as a restrictor. The oil then flows downward, through the hollow center tube, and out the bottom, where it is piped to the governor. (Or back to the crankcase, on older models.) No restrictor should be needed at the governer. There have been questions, however, if any of the filter canisters had a restriction at the inlet fitting also. I cannot answer that with certainty. If you'd like more info on new pumps and the need to align bore, email me.
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